Catalytic ignition device for gas



June 20, 1939. A. B. DENSHAM CATALYTIC IGNLTION DEVICE FOR GAS BURNERS Filed Aug. 19, 1935 Patented June 20, 1939 amazes L cA'rAmmc rcm'rron nnvrcn roa GAS k BURNERS Alec Bramley Densham, London, England, as-

signor to The Gas Light and Coke Company, Westminster, London, England, a British com:

Application August 19, 1935, Serial No. 36,887

In Great Britain August 24., 1934 4 Claims. (Cl. 158-115) This invention is for improvements in or relating to catalytic ignition devices for gas burners. It has already been proposed to associate with a gas burner a chamber containing a catalyst. which chamber has been formed from metal and has been so ,disposed as to receive a part of the gaseous mixture issuing from the unlit burner. The action of such devices has heretofore been somewhat uncertain owing to the fact that no attempt has been made to ensure that the correct gas and air mixture reaches the catalyst, and due to the fact that the heat generated by the catalyst and by the partly-lit mixtures has been conducted away by the walls of the chamber whereby ignition of the mixture of the gas as a whole has been prevented.

According to this invention, a catalytic ignition device for a gas burner comprises a chamber formed from a material of low thermal conductivity and low thermal capacity (from a material such as a porous refractory brick), a catalyst located in said chamber, which chamber is provided with an inlet opening so disposed and directed as to receive a supply of gaseous mixture from an auxiliary jet associated with the burner and with a second opening so disposed as to promote a flow of mixture past said catalyst. It will be appreciated that owing to the nature of the material from which the chamber is formed the catalyst may be located near the burner without being unduly heatedby the gas flame.

An important constructional form of the invention comprises a chamber located to one side of said burner, a catalyst disposed therein, which chamber is provided with an inlet opening for receiving a gaseous mixture, an auxiliary jet on said burner or on a conduit communicating with the burner and arranged to direct a gaseousmixture through said opening and an outlet opening insaid chamber arranged to promote a flow of gaseous mixture past said catalyst. The jet is arranged to direct a horizontal stream of gas into the housing and is disposed at such a distance therefrom that as soon as the stream becomes ignited the flame curls upwardly in front of the housing and is thus prevented from damaging the catalyst, but is usefully employed for heating purposes. Preferably, said jet is removable so that the size of jet may be initially selected in accordance withthe set of conditions under which the apparatus is to be used, and in order to ensure that the correct strength of mixture enters said chamber. It has been .found in practice with town's gas containing approximately 50% of hydrogen that it is important for the. gas mixture in the neighbourhood of the catalyst to contain from 12 to 20% of gas, in order that the most eifective operation of the device may be obtained. The provision of a special jet, as distinct from employing one of the nozzles of the burner as heretofore, not only enables the required strength of mixture to be obtained, but renders the supply less liable to variation.

Two embodiments of the present invention are now described with reference to the accompanying drawing, in which:

Figure 1 shows a cut-away view of a hot-plate burner, to which one embodiment of the invention is applied.

.Figure 2 shows in section the disposition of an auxiliary jet and a catalyst housing,

Figure 3 is an elevation of the catalyst housing,

Figure 4 is a section along the line 4-4 of Figure 3,

Figure 5 is a perspective view of another embodiment of the invention as applied to a gasflre, and

Figure 6 is a plan view of an auxiliary jet shown in Figure 5.

A hot-plate burner is shown in Figure 1 and comprises the usual gas ring l having the jets' II disposed in the usual manner. The burner is carried on a conduit I2 which has formed on the upper surface thereof a flat platform I3. On the end of the platform nearest the gas ring there is provided an upstandingbase l4 formed with a hole which is screw-threaded to receive an auxiliary jet I;the orifice I6 (Figure 2) of this jet is directed towards the opening in a housing ll for a catalyst, which housing is formed of a material having a low thermal conductivity and a low thermal capacity. The use of a material having a low thermal conductivity and a low thermal capacity prevents the heat generated by the action of the air gas mixture from being conducted away too rapidly, while the surrounding walls heat up rapidly and thereby reduce the loss of the heat from the catalyst by radiation; furthermore, the low thermal conductivity material protects the catalyst from the harmful effect of prolonged heating, and thereby ensures a longer life of the catalyst. The housing as shown in elevation in Figure} is provided with openings at the front and back and is approximately 1%" long, ii" high at the rearmost end and high at the front, whilst the front orifice is high and the rear is approximately in height. The passageway I9 through this housing slopes gradually from the back downwardly towards the front and is approximately wide. Towards the rear end of this passageway and about mid-way up there are provided two grooves it, one on either side, in which acatalyst frame 20 is located. The relative positions of the auxiliary jet and the housing are'shown in Figure 2 and it is found that the best results are obtained when the jet is' disposed about 1%" Ill platinum black supported on a pellet of porous material which is suspended by platinum wires 23 from the catalyst frame 20.

In Figure 5 there is shown another method of applying the invention to a gas fire in which there is the usual gas supply-pipe 24 running along the lower part of a gas fire frame 25 and having the usual gallery 25 on which the radiants are supported. An upright pipe 21 leads out of the supply-pipe 24 and carries at its upper end a litment 28 having a number of holes 29 and 30, certain of which are of small size (29) and are directed towards the catalyst housing II which is similar to that shown in Figures 3 and 4. Figure 6 is a plan view of the fitment 28 and shows the disposition of the holes 29 and '30 which are preferably radially disposed from one another at an angle of The operation of the catalytic igniting device in both the above-described constructions is the same: the gas stream'lssues out of the jet iii in Figure 2 or from the holes 29 in Figure 5 and passes, in admixture with air, into the housing l1 and flows over the blob 22 of platinum black, This blob first glows, due to the slow combustion of the gas and air, and the heat from the blob is transferred to-the platinum wires 23, which cause the gas admixture to ignite. The flame then strikes back to the jet IE, or to the small holes 29 in Figure 5.

In the construction shown in Figure 1, owing to the heat of the burning gas issuing from the jet IS, the flame curls upwardly and the several jets ll of the gas ring ill become ignited. It will be appreciated that with this arrangement the catalyst is not heated whilst the burner is alight. 1

In the construction shown in Figure 5, the gas which has passed into the housing strikes back to the small holes 29 and the gas issuing from the larger orifice 30 is then ignited. The

flame from the orifice 30 is directed towards the fuel blocks 32 through which the gas from the burners 3| is passing, whereby the gas is ignited. In this construction, as in the construction shown in Figure 1, the catalyst is not heated whilst the gas fire is in operation owing to the fact that the small flames from the orifices 29 are diverted upwardly.

I claim:

1. A gas heater comprising a burner tube having a number of main burner jets and an auxiliary jet, means for supplying said burner tube and jets with an air-gas mixture, a catalyst chamber formed from a material of low thermal conductivity and having a passageway between inlet and outlet openings, 8. catalyst disposed in said throughway, which catalyst chamber is disposed out of the-path of flow of the main jets and out of the path of flow of the ignited gases issuing from the auxiliary jet but with its inlet opening opposite and distant from said auxiliary jet, whereby additional air is entrained in the airgas mixture issuing from'the auxiliary jet and whereby a steady stream of the diluted unignited air-gas mixture is directed over the catalyst and the flame resulting from the combustion of the mixture is directed towards said jets.

2. A gas heater comprising a burner tube having a number of main burner jets, a plurality of radiants mounted above said jets, an auxiliary jet, means for supplying said jets with air-gas jets, having a throughway between inlet and out- 7 let openings, a catalyst disposed in said through way, which catalyst chamber is disposed out of the path of flow of the main jets and out of the path of fiow oi ignited gases issuing from the auxiliary jet and which auxiliary jet is provided with at least one orifice directed towards said inlet opening in the catalyst chamber and another orifice directed towards the main burner jets, whereby additional air is entrained in the airgas mixture issuing from the auxiliary jet and whereby a steady stream of the diluted unignited air-gas mixture is directed over the catalyst and the flame resulting from the combustion of the mixture is directed towards the auxiliary jet which then lights the main jets.

3. A gas heater comprising a burner tube having a, main burner with a plurality of jets and an auxiliary jet adjacent the main burner, means for supplying the burner tube and jets with an airgas mixture, a catalyst chamber made from material having low thermal capacity and low thermal conductivity and having an inlet opening and an outlet opening and a passageway connecting said inlet and outlet openings, a catalyst disposed in said passageway, said catalyst chamber being disposed out or the path of flow of the main jets and distant from the main jet and the auxiliary jet and in position to receive a supply of air-gas mixture from the auxiliary'jet, said auxiliary jet and the spacing of the auxiliary jet from the inlet opening of the catalyst chamber being such that additional air is entrained in the air-gas mixture issuing from the auxiliary jet so that the mixture which passes through the pas-' sageway in the catalyst chamber is of predetermined portions of air and gas, and the flame resulting from the combustion of the mixture is directed toward the auxiliary jet and the main jet.

4. A gas heater comprising a burner tube having a main burner witha plurality of jets and an auxiliary jet adjacent the main burner, means for supplying the burner tube and jets with an air-gas mixture, a catalyst chamber made from material having low thermal capacity and low thermal conductivity and having an inlet opening and an outlet opening and a passageway connecting said inlet and outlet openings, a catalyst disposed in said passageway, said catalyst chamber being disposed out of the path of flow of the main jets and distant from the main jet and the auxiliary jet and out of the path of flow of ignited gases issuing from the auxiliary jet and in position to receive a supply of air-gas mixture from the auxiliary jet, upstanding walls extending from the inlet opening of the catalyst chamber to a point adjacent the auxiliary jet to form an open-mouthed trough, said auxiliary jet and the spacing of the auxiliary jet from the inlet opening of the catalyst chamber being such that additional air is entrained in the air-gas mixture issuing from the auxiliary jet so that the mixture which passes through the passageway in the catalyst chamber is of predetermined portions of air and gas, and the flame resulting from the combustion of the mixture is directed toward the auxiliary jet and the main jet.

ALEC BRAMLEY DENSHAM. 

